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      <h2><a href="./">Go by Example 中文版</a>: 指针</h2>
      
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            <p>Go 支持 <em><a href="http://zh.wikipedia.org/wiki/%E6%8C%87%E6%A8%99_(%E9%9B%BB%E8%85%A6%E7%A7%91%E5%AD%B8)">指针</a></em>，
允许在程序中通过 <code>引用传递</code> 来传递值和数据结构。</p>

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            <a href="http://play.golang.org/p/J5qGHVGN1A4"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
          <div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
</pre></div>

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          <div class="highlight"><pre><span class="kn">import</span> <span class="s">&quot;fmt&quot;</span>
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            <p>我们将通过两个函数：<code>zeroval</code> 和 <code>zeroptr</code> 来比较 <code>指针</code> 和 <code>值</code>。
<code>zeroval</code> 有一个 <code>int</code> 型参数，所以使用值传递。
<code>zeroval</code> 将从调用它的那个函数中得到一个实参的拷贝：ival。</p>

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          <div class="highlight"><pre><span class="kd">func</span> <span class="nx">zeroval</span><span class="p">(</span><span class="nx">ival</span> <span class="kt">int</span><span class="p">)</span> <span class="p">{</span>
    <span class="nx">ival</span> <span class="p">=</span> <span class="mi">0</span>
<span class="p">}</span>
</pre></div>

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            <p><code>zeroptr</code> 有一个和上面不同的参数：<code>*int</code>，这意味着它使用了 <code>int</code> 指针。
紧接着，函数体内的 <code>*iptr</code> 会 <em>解引用</em> 这个指针，从它的内存地址得到这个地址当前对应的值。
对解引用的指针赋值，会改变这个指针引用的真实地址的值。</p>

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          <div class="highlight"><pre><span class="kd">func</span> <span class="nx">zeroptr</span><span class="p">(</span><span class="nx">iptr</span> <span class="o">*</span><span class="kt">int</span><span class="p">)</span> <span class="p">{</span>
    <span class="o">*</span><span class="nx">iptr</span> <span class="p">=</span> <span class="mi">0</span>
<span class="p">}</span>
</pre></div>

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          <div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
    <span class="nx">i</span> <span class="o">:=</span> <span class="mi">1</span>
    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;initial:&quot;</span><span class="p">,</span> <span class="nx">i</span><span class="p">)</span>
</pre></div>

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          <div class="highlight"><pre>    <span class="nx">zeroval</span><span class="p">(</span><span class="nx">i</span><span class="p">)</span>
    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;zeroval:&quot;</span><span class="p">,</span> <span class="nx">i</span><span class="p">)</span>
</pre></div>

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            <p>通过 <code>&amp;i</code> 语法来取得 <code>i</code> 的内存地址，即指向 <code>i</code> 的指针。</p>

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          <div class="highlight"><pre>    <span class="nx">zeroptr</span><span class="p">(</span><span class="o">&amp;</span><span class="nx">i</span><span class="p">)</span>
    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;zeroptr:&quot;</span><span class="p">,</span> <span class="nx">i</span><span class="p">)</span>
</pre></div>

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            <p>指针也是可以被打印的。</p>

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          <div class="highlight"><pre>    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;pointer:&quot;</span><span class="p">,</span> <span class="o">&amp;</span><span class="nx">i</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>

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            <p><code>zeroval</code> 在 <code>main</code> 函数中不能改变 <code>i</code> 的值，
但是 <code>zeroptr</code> 可以，因为它有这个变量的内存地址的引用。</p>

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          <div class="highlight"><pre><span class="gp">$</span> go run pointers.go
<span class="go">initial: 1</span>
<span class="go">zeroval: 1</span>
<span class="go">zeroptr: 0</span>
<span class="go">pointer: 0x42131100</span>
</pre></div>

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      codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import \"fmt\"\u000A');codeLines.push('func zeroval(ival int) {\u000A    ival = 0\u000A}\u000A');codeLines.push('func zeroptr(iptr *int) {\u000A    *iptr = 0\u000A}\u000A');codeLines.push('func main() {\u000A    i := 1\u000A    fmt.Println(\"initial:\", i)\u000A');codeLines.push('    zeroval(i)\u000A    fmt.Println(\"zeroval:\", i)\u000A');codeLines.push('    zeroptr(&i)\u000A    fmt.Println(\"zeroptr:\", i)\u000A');codeLines.push('    fmt.Println(\"pointer:\", &i)\u000A}\u000A');codeLines.push('');
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